I think the slight difference in real-world sharpness is secondary to the difference in closest focusing distance. Remember the 135mm doesn't let you get closer than 3 feet from your subject, which, IMO, really makes it a more specialized lens--portraits, some street photography, landscape panoramas...
I wouldn't sell either my ef 100mm 2.8 macro (non-L) or my 135 because they are so very different. I always bring the macro on a nature hike, but I never use it for portraits. I love the colors, contrast, and bokeh of the 135mm too much.
If you are doing events, remember you can't easily get good detail shots (without lots of cropping) with the 135. In fact, for weddings, presentations, etc, the 135mm is often limited to set-up type shots, because you have a fixed focal length and have to remain at least 3 feet from your subjects. With something like a 70-200mm, you have about the same MFD, but more options with focal length.
If you really love portraits, the 135mm may be Canon's very best value. It is very sharp at f/2, and so sharp at f/2.8 and up that pores and little problems with makeup become a real issue in Photoshop.